Mirrors: Reflection and Transmission

(A Scratch program for simulating optics)

Heather

work experience
2009

In this example, the grey-blue rectangle in the middle is representing a mirror. This is a piece of glass which has been treated to allow more or less light to be reflected. The red arrows are light rays. So when the first arrow hits the mirror, some of it is reflected and some of it passes through (is transmitted), though the amount reflected and the amount passing through is affected by the reflectivity and transmission. So for example:

  • The higher the reflectivity and lower the transmission the more light is reflected, so the red arrow being reflected is darker, and the red arrow passing through is more transparent.
  • The lower the reflectivity, and the higher the transmission, more light passes through, so the arrow passing through is darker, and the arrow being reflected is more transparent.

In the program below, you can change the amount of reflectivity by moving the slider, which automatically changes the transmission. This then changes the transparency of the arrows passing through and being reflected, although in reality you could not change the reflectivity like that, you would have to order a mirror with a certain amount of reflectivity. This is a lossless mirror, so the reflection plus transmission is always equal to 100%, so no light is lost.

 
You can download Scratch and the source code for this program.